Blizzard Entertainment, the California-based gaming giant behind World of Warcraft and Diablo III, has confirmed that its internal network was attacked by hackers. In a message to users today, Blizzard president Mike Morhaime said the extent of the breach appears to be confined to email addresses and scraps of Battle.net log-in information – credit card numbers, billing addresses, and real names were reportedly not exposed.

"Some data was illegally accessed, including a list of email addresses for global Battle.net users, outside of China," Morhaime wrote. "For players on North American servers, the answer to the personal security question, and information relating to Mobile and Dial-In Authenticators were also accessed. Based on what we currently know, this information alone is NOT enough for anyone to gain access to Battle.net accounts."

So how many players use North American servers? Well, according to Morhaime, it's not just North Americans – players in Latin America, Australia, New Zealand, and Southeast Asia would all be affected. The precise nature and timing of the attack remain unclear, but Blizzard says it is currently working with law enforcement and security experts to investigate the incident.

Assuming you're a Battle.net user in one of the areas listed above, the first thing you should do is change your password. The link is here. If your Battle.net log-in is the same as your email or Twitter or Facebook log-in, you should change that information, too. (In fact, even if you're not a Battle.net user, you should get into the habit of running different passwords and log-ins on different accounts.)

In related news, earlier this month Morhaime revealed that during Q2 of 2012, the number of World of Warcraft subscribers shrank from 10.2 million to 9.1 million – a plunge he attributed to the lack of new content. He also pointed to the remedy: Mists of Pandaria, an expansion pack launching on Sept. 25.